Mobile telecommunications system

ABSTRACT

A method of processing a handover request from a base station controller (BSC) of a GSM (Global System for Mobile communication)-type network. The method comprises the steps of passing a handover request with GSM-type parameters from a base station controller (BSC) through a Master Switching Center (MSC) of the GSM-type network to a UMTS core network (CN) and to a Radio Network Controller (RNC) of the UMTS (Universal Mobile Telecommunications System) network, translating the GSM-type parameters to UTRAN parameters in the Radio Network Controller (RNC), and allocating UTRAN resources in response to the translated parameters.

BACKGROUND OF THE INVENTION

The present invention relates to a mobile telecommunication system andis particularly concerned with the handover of calls between two typesof communication system, particularly handover between a GSM and a UMTSnetwork.

It has been generally proposed that it would be desirable to providehandover between a GSM network and a UMTS network. However, this is nota straightforward task to accomplish and there are a number of problemsto implement before this can be successfully achieved; the presentinvention is concerned with these problems. It is, however, moregenerally applicable to interoperability between networks usingdifferent protocols; in such a case, the terms used herein are to beconstrued as applying to the relevant equivalent components of thenetworks to which the invention is applied. Although aspects of theinvention provide independent solutions to various aspects of theproblems concerned with GSM to UMTS handover, all are concerned withthis common problem and in particular are concerned with a particularnovel solution in which an RNC of the UMTS network controls handover toa large extent.

The invention is described in the context of GSM and UMTS networks forease of understanding but is applicable to handover between othernetworks with similar characteristics. Accordingly, all references toGSM and UMTS and all terms of art used herein are to be construed asencompassing equivalent features of other networks. In particular, thepresent Japanese PDC network is of similar architecture to GSM and theterm GSM (or GSM-type) as used in the specification and claims isintended to encompass such a network. Similarly, the term UMTS (andrelated terms) is intended to encompass a UMTS system in accordance withpresent standards and proposals and any derivatives or equivalentsthereof.

SUMMARY OF THE INVENTION

In a first aspect, the invention provides a method of processing ahandover request from a base station controller (BSC) of a GSM network,the method comprising passing a handover request with GSM parametersfrom a base station controller (BSC) through a Master Switching Centre(MSC) of the GSM network to a UMTS core network (CN) and to a RadioNetwork Controller (RNC) of the UMTS network; in the radio networkcontroller, translating the GSM parameters to UTRAN parameters; andallocating UTRAN resources in response to the translated parameters.Thus, rather than translating the GSM parameters on entry to the UMTSnetwork, the GSM parameters pass transparently through at least aportion of the UMTS network to the RNC. The parameters may include oneor more of data rate, call type (voice, data, fax, other, e.g. video,IP), Quality of Service etc. This reduces processing load elsewhere inthe network and enables the RNC to allocate the optimum UTRAN resourcesfor the call.

Preferably, the RNC is arranged to switch directly from a GSM connectionto a soft handover UMTS mode. This is advantageous compared to simplyestablishing an individual connection from the User Equipment (UE) to asingle UMTS access node. This preferred features may be providedindependently in a second aspect in which the invention provides amethod of switching from a GSM network to a UMTS network characterisedby switching directly from a mode in which User Equipment (UE) is incommunication with a GSM base station to a UMTS diversity mode in whichthe User Equipment is in communication with a plurality of UMTS accessnodes, preferably comprising configuring the UTRAN so that a pluralityof access nodes are prepared to communicate with the UE and/orpreferably supplying a list of potential access nodes to the UE.

Preferably, the Radio Network Controller (RNC) is arranged, followingtranslation of the GSM format handover request firstly to perform radiolink setup and then, following a response from the radio link, toperform data transport setup for communication between the Radio NetworkController and the Core Network. This allows communication with the CoreNetwork to be established following successful radio setup rather thanindependently, thus avoiding unnecessary use of CN to RNC (Iu interface)resources if radio link setup is not possible. This preferable featuremay be provided independently in a third aspect in which the inventionprovides a method of establishing UMTS communication with User Equipmentfollowing receipt by a Radio Network Controller of a GSM handoverrequest, the method comprising, in the Radio Network Controller, settingup a radio link to a Node B and, following acknowledgement of the radiolink setup, in the Radio Network Controller, setting up data transportbetween the Radio Network Controller and the Core Network.

Preferably, the Radio Network Controller is arranged (preferablyfollowing radio link setup) to pass a handover message containing UTRANparameters through the GSM network (for example as a message),preferably through the Core Network to the GSM Master Switching Centreand preferably at least through the Base Station Controller of the GSMnetwork, to the User Equipment; the method further comprisinginterpreting the UTRAN parameters in the User Equipment and, in responseto the parameters, initiating communication between the User Equipmentand the UMTS network.

This may be provided independently in a fourth aspect in which theinvention provides a method of establishing UMTS communication betweenUser Equipment and a UMTS network, wherein the User Equipment is incommunication with a GSM network, the method comprising forwarding UTRANparameter information, preferably comprising a list of potential UMTSAccess Nodes via the GSM network, preferably from a Radio NetworkController of the UMTS network, to the User Equipment and, in the UserEquipment, interpreting the UTRAN parameter information and initiatingcommunication with the UMTS network.

Thus, in contrast to the initial step, where GSM information tunnelsinto the UMTS network and is interpreted in the RNC, the UTRANinformation tunnels through the GSM network without interpretation andis interpreted by the UE. This means that the GSM network need notinclude intelligence to process the information, simplifyinginterconnection with existing GSM networks.

Following initiation of communication, preferably the UE is arranged toestablish a link through the RNC of the UMTS network to the MSC of theGSM network (where the GSM call originated). This then completesestablishing a link from the MSC to the UE via the UMTS network.

Preferably, potential links supplied in a list to the UE on whichsatisfactory communication is not possible are deleted from the list ofavailable links; this step may be provided independently in a method ofperforming soft handover from a GSM network to a UMTS network comprisingsupplying a list of potential UMTS access nodes to User Equipment;establishing communication between the UE and at least one UMTS accessnode; and deleting potential nodes with which satisfactory communicationis not possible from said list.

Preferably, at least during handover, the User Equipment (UE) isarranged to communicate over both the GSM network and the UMTS networksimultaneously or quasi-simultaneously. This feature may be providedindependently in a fifth aspect in which the invention provides a methodof communicating between User Equipment and GSM and UMTS networkscomprising communicating information simultaneously orquasi-simultaneously via both networks during handover from one networkto the other.

All of the above aspects may be provided independently, but areadvantageously combined in a system. Thus, the invention may provide amethod of handing over a GSM call to a UMTS network comprising: passinga handover request from the GSM network (preferably from a BSC,preferably containing GSM call parameters) to a RNC of the UMTS network;interpreting the request in the RNC and initiating call setup(preferably performing radio link setup and preferably thereafter, inresponse to a successful setup, performing data link to core networksetup); forwarding handover information containing UTRAN parameters(preferably including a list of potential access nodes) to UE(preferably passing the UTRAN information transparently through the GSMnetwork, for example as a message, to be interpreted by the UE); in theUE, setting up a UMTS call based on the UTRAN parameters.

The invention extends to a radio network, or combination of networks,radio network components, particularly RNCs and UEs all adapted toimplement any of the above method aspects.

BRIEF DESCRIPTION OF THE DRAWING

An embodiment of the invention will now be described, with reference tothe accompanying drawing in which FIG. 1 depicts the sequence of eventsbetween GSM to UMTS handover via a MAP/E interface. This will also beapplicable via the IWU.

DESCRIPTION OF THE PREFERRED EMBODIMENT

1. The BSC sends Handover Required message to the GSM MSC. This includesthe GSM information elements {service information rate, service type,etc.} and the UMTS cell/Node-B information on which good radio qualityis achievable.

2. The GSM MSC sends MAP/E message Prepare Handover to the UMTS CNforwarding the UMTS cell-ids transparently.

3. The CN sends RANAP message Handover Request to the Target RNC. Thismessage will contain information elements indicating from which networktype this handover is taking place e.g. ‘handover-type’=‘from GSM’. Itwill also contain information elements allowing transparent transfer ofGSM Parameters to the RNC, e.g. GSM Bearer Capability, version numberand other relevant parameters relating to the GSM call. Additionally,the relevant UMTS cell/Node-B information provided by the MS/UE is alsotransferred transparently to the RNC.

4. The RNC maps GSM appropriate call parameters to the relevant UMTSlogical channel, transport channel and allocates radio resourceparameters as appropriate (e.g. DL channelization code, UL spreadingfactor, UL scrambling code, Radio Frequency, Radio Link ID, LinkReference, S-RNTI, Transport Format Sets, Transport Format CombinationSet, Initial DL Power). This function can only be done at this stage,since only the RNC knows the status of the radio resources.

5. Since dedicated transport channels are selected, the GSM call can gointo immediate soft-handover.

i) The RNC sends NBAP message Radio Link Setup to all relevant Node Bs.

ii) All relevant Node Bs start transmission/reception.

iii) All relevant Node Bs send NBAP message Radio Link Setup Response tothe RNC.

6. The RNC sets up Iub transport bearer to all relevant Node Bs. The RNCis in a condition to set up the Transport Bearer across Iub since itknows if the UTRAN resources have been set up successfully.

7. The RNC sets up Iu transport bearer. The RNC is in a condition to setup the Transport Bearer across Iu since it knows if the UTRAN resourceshave been set up successfully.

8. The RNC sends Handover Request Acknowledge passing the appropriateUMTS parameters to the CN (e.g. DL channelization code, UL SpreadingFactor, UL Scrambling Code, etc.) which are destined for the UE allowingthe successful handover of the UE to UMTS.

9. The CN sends Prepare Handover Response to the GSM MSC (forwarding theUMTS parameters).

10. The GSM MSC sends Handover Command to the BSC (forwarding the UMTSparameters).

11. BSC sends the RR message Handover Command to the UE. This containsthe necessary UMTS parameters.

12. The UE interprets the UMTS parameters within the RR message and isable to switch the call from a GSM call into a UMTS call with multipleor single diversity branches as indicated in the UMTS parameters. Atthis stage, the mobile unit is receiving information from the GSMnetwork using its GSM capabilities and uses this information to switchcommunication to the UMTS network or simultaneously communicate with theUMTS network and GSM network using its UMTS and GSM capabilities.

13. The UE starts Tx/Rx.

14. On detection of synchronisation, the Node B sends NBAP messageHandover Detect to the RNC.

15. If at least one of the Radio links has been successfully set up,then the RNC is able to establish the RLC link for the DTCH and the RRCfor the DCCH to the UE. The RNC is then able to signal to the CN andonwards to the MSC that the handover is complete. The MSC is able toswitch the call through on the new UTRAN leg.

16. In the case of having allocated multiple radio links on the DL andif UL synchronisation has not been detected, then the appropriatesignalling may take place between Node B and RNC to release the unusedradio resources.

It will be appreciated that the invention can be applied to othernetwork configurations. To assist in appreciating how the invention maybe extended, a glossary of terms used in the art pertaining to UMTSsystems is provided; any of the terms of art may be replaced byfunctionally equivalent components in a non-UMTS system. The followingdocuments are incorporated herein by reference:

[1]Draft-ETR/SMG-50102, “Special Mobile Group (SMG) Vocabulary for theUniversal Mobile Telecommunications System”.

[2]ETSI DTR/SMG-0225xxU, “Universal Mobile Telecommunications System(UMTS); Vocabulary for the UTRAN”, UMTS 25.XX Version 0.1.0.

Terms and Definitions

Active Set

Set of radio links simultaneously involved in a specific communicationservice between a UE and a UTRAN.

Cell

A cell is a geographical area that can be identified by a UE from a(cell) identification that is broadcast from one UTRAN Access Point.

Coded Composite Transport Channel (CCTrCH)

A data stream resulting from encoding and multiplexing of one or severaltransport channels.

The data stream of the CCTrCH is fed to a data splitter unit that splitsthe CCTrCH's data stream onto one or several Physical Channel DataStreams.

Contention Resolution

A functionality or procedure to solve the collision of identities on theinitial random access messages from two (or more) UEs.

Forward Handover

A type of handover initiated by the UE. The UE sends the request forestablishment of a new radio link in the new cell, i.e. it does not usethe current radio link for performing handover but a radio link of thenew cell.

Gateway UE_(R)/Seed

A ODMA relay node that also communicates with the UTRAN using either TDDor FDD mode.

Handover

Handover is a family of procedures that adds or removes one or severalradio links between one UE and UTRAN when a RRC connection exists andthe position of the UE is known on cell level in the UTRAN.

Hard Handover

Hard handover is a category of handover procedures where all the oldradio links in the UE are abandoned before the new radio links areestablished.

Logical Channel

A logical channel is an information stream dedicated to the transfer ofa specific type of information over the radio interface.

ODMA Relay Node

A relay device, such as a UE_(R) or Seed, that is capable of relayingusing the ODMA protocol.

Physical Channel

In FDD mode, a physical channel is defined by code, frequency and, inthe uplink, relative phase (I/Q). In TDD mode, a physical channel isdefined by code, frequency, and time-slot.

Physical Channel Data Stream

In the uplink, a data stream that is transmitted on one physicalchannel.

In the downlink, a data stream that is transmitted on one physicalchannel in each cell of the active set.

Radio Access Bearer

The service that the access stratum provides to the non-access stratumfor transfer of user data between UE and CN.

Radio Frame

A radio frame is a numbered time interval of 10 ms duration used fordata transmission on the radio physical channel. A radio frame isdivided into 16 time slots of 0.625 ms duration. The unit of data thatis mapped to a radio frame (10 ms time interval) may also be referred toas radio frame.

Radio Link

The set of (radio) physical channels comprised in a transmission pathbetween a UE to one UTRAN access point.

Radio Link Addition

The procedure where a new radio link is added to the active set.

Radio Link Removal

The procedure where a radio link is removed from the active set.

Radio Network Temporary Identifier (RNTI)

A Radio Network Temporary Identifier is an identifier for a UE when anRRC connection exists. It is e.g. used by the MAC protocol on commonTransport Channels (RACH, FACH, PCH).

Relay

A device capable of receiving and transmitting information for anotheruser.

Relaying

The process of receiving and transmitting information for another user,such as carried out by a UE_(R).

Relaylink

Relaylink is the communications line between two ODMA relay nodes.

Root Relay

ODMA relay node where communications are either sourced or sunk.

RRC Connection

A point-to-point bi-directional connection between RRC peer entities onthe UE and the UTRAN sides, respectively. An UE has either zero or oneRRC connection.

Seed

A ODMA relay node which is deployed by a network operator and isgenerally fixed, constantly powered, and has no display/keypad.

Signalling Connection

An acknowledged-mode link between the user equipment and the corenetwork to transfer higher layer information between peer entities inthe non-access stratum.

Signalling Link

Provides an acknowledged-mode link layer to transfer the UE-UTRANsignalling messages as well as UE—Core Network signalling messages(using the signalling connection).

Soft Handover

Soft handover is a category of handover procedures where the radio linksare added and abandoned in such manner that the UE always keeps at leastone radio link to the UTRAN.

Transmission Time Interval

Transmission Time Interval is defined as the inter-arrival time ofTransport Block Sets, i.e. the time it should take to transmit aTransport Block Set. It is always a multiple of 10 ms (the length of oneRadio Frame).

Transport Block

Transport Block is defined as the basic unit passed down to L1 from MAC,for L1 processing. An equivalent term for Transport Block is “MAC PDU”.

Transport Block Set

Transport Block Set is defined as a set of Transport Blocks which ispassed to L1 from

MAC at the same time instance using the same transport channel. Anequivalent term for Transport Block Set is “MAC PDU Set”.

Transport Block Set Size

Transport Block Set Size is defined as the number of bits in a TransportBlock Set.

Transport Block Size

Transport Block Size is defined as the size (number of bits) of aTransport Block

Transport Channel

The channels offered by the physical layer to Layer 2 for data transportbetween peer L1 entities are denoted as Transport Channels.

Different types of transport channels are defined by how and with whichcharacteristics data is transferred on the physical layer, e.g. whetherusing dedicated or common physical channels are employed.

Transport Format

A Transport Format is defined as a format offered by L1 to MAC for thedelivery of a Transport Block Set during a Transmission Time Interval ona Transport Channel. The Transport Format constitutes of two parts—onedynamic part and one semi-static part.

Transport Format Combination

A Transport Format Combination is defined as the combination ofcurrently valid Transport Formats on all Transport Channels of a UE,i.e. containing one Transport Format from each Transport Channel.

Transport Format Combination Set

A Transport Format Combination Set is defined as a set of TransportFormat Combinations to be used by a UE.

Transport Format Combination Indicator (TFCI)

A Transport Format Combination Indicator is a representation of thecurrent Transport Format Combination.

Transport Format Indicator (TFI)

A label for a specific Transport Format within a Transport Format Set.

Transport Format Set

A Transport Format Set is defined as the set of Transport Formatsassociated to a Transport Channel.

URA Updating

URA updating is a family of procedures that updates the UTRANregistration area of a UE when a RRC connection exists and the positionof the UE is known on URA level in the UTRAN.

User Equipment/Relay Enabled (UE_(R))

A UE with ODMA relay operation enabled.

UTRAN Registration Area (URA)

The UTRAN Registration Area is an area covered by a number of cells. TheURA is only internally known in the UTRAN.

UTRAN Access Point

A conceptual point within the UTRAN performing radio transmission andreception. A UTRAN access point is associated with one specific cell,i.e. there exists one UTRAN access point for each cell. It is theUTRAN-side end point of a radio link.

Abbreviations ARQ Automatic Repeat Request BCCH Broadcast ControlChannel BCH Broadcast Channel BPSK Binary Phase Shift Keying BSS BaseStation System BTS Base Transceiver Station C- Control- CC Call ControlCCCH Common Control Channel CCH Control Channel CCTrCH Coded CompositeTransport Channel CDMA Code Division Multiple Access CN Core Network CRCCyclic Redundancy Check DC Dedicated Control (SAP) DCA Dynamic ChannelAllocation DCCH Dedicated Control Channel DCH Dedicated Channel DHODiversity Handover DL Downlink DRNC Drift Radio Network ControllerDS-CDMA Direct-Sequence Code Division Multiple Access DSCH DownlinkShared Channel DTCH Dedicated Traffic Channel DTX DiscontinuousTransmission FACH Forward Link Access Channel FAUSCH Fast UplinkSignalling Channel FCS Frame Check Sequence FDD Frequency DivisionDuplex GC General Control (SAP) HO Handover HHO Hard Handover ITUInternational Telecommunication Union kbps kilo-bits per second kspskilo-symbols per second L1 Layer 1 (physical layer) L2 Layer 2 (datalink layer) L3 Layer 3 (network layer) LAC Link Access Control MACMedium Access Control MM Mobility Management Mcps Mega-chips per secondNt Notification (SAP) OCCCH ODMA Common Control Channel ODCCH ODMADedicated Control Channel ODCH ODMA Dedicated Channel ODMA OpportunityDriven Multiple Access ORACH ODMA Random Access Channel ODTCH ODMADedicated Traffic Channel PCCH Paging Control Channel PCH Paging ChannelPDU Protocol Data Unit PHY Physical layer PhyCH Physical Channel RACHRandom Access Channel RLC Radio Link Control RNC Radio NetworkController RNS Radio Network Subsystem RNTI Radio Network TemporaryIdentity RRC Radio Resource Control SAP Service Access Point SCCHSynchronization Control Channel SCH Synchronization Channel SDU ServiceData Unit SIR Signal-to-Interference Ratio SRNC Serving Radio NetworkController SRNS Serving Radio Network Subsystem TCH Traffic Channel TDDTime Division Duplex TFCI Transport Format Combination Indicator THTransport Format Indicator TN Termination Node TPC Transmit PowerControl TRX Transmitter/Receiver U- User- UE User Equipment UE_(R) UserEquipment with ODMA relay operation enabled UL Uplink UMTS UniversalMobile Telecommunications System URA UTRAN Registration Area UTRA UMTSTerrestrial Radio Access UTRAN UMTS Terrestrial Radio Access Network

What is claimed is:
 1. A method of processing a handover request from abase station controller of a Global System for Mobile communicationnetwork, comprising: passing a handover request with Global System forMobile communication parameters from a base station controller through amaster switching center of the Global System for Mobile communicationnetwork to a UMTS core network and through the UMTS core network whilebeing maintained in said Global System for Mobile communicationparameters to a radio network controller located within the UMTS corenetwork; translating, in the radio network controller, the Global Systemfor Mobile communication parameters to UTRAN parameters; and allocatingUTRAN resources in response to the translated parameters.
 2. A methodaccording to claim 1, wherein the parameters include one or more of datarate, call type and Quality of Service.
 3. A method according to claim1, wherein allocating UTRAN resources comprises: setting up a radio linkto a node in the radio network controller; and, setting up datatransport between the radio network controller and the UMTS core networkin the radio network controller following acknowledgement of the radiolink setup from the node.
 4. A method of establishing UMTS communicationwith user equipment following receipt by a radio network controller of aGlobal System for Mobile communication handover request, comprising:setting up a radio link to a node in the radio network controller;setting up data transport between the radio network controller and theUMTS core network following acknowledgement by the radio networkcontroller of the radio link setup from the node; and translating, inthe radio network controller, Global System for Mobile communicationparameters to UTRAN parameters.
 5. A method of establishing UMTScommunication between user equipment and a UMTS network, wherein theuser equipment is in communication with a Global System for Mobilecommunication network, comprising: forwarding UTRAN parameterinformation to the user equipment via the Global System for Mobilecommunication network; and interpreting the UTRAN parameter informationand initiating communication with the UMTS network in the userequipment; supplying a list of potential UTRAN access points to the userequipment; establishing communication between the users equipment and atleast one UTRAN access point; and deleting from said list potentialUTRAN access points the access points with which satisfactorycommunication is not possible.
 6. A method according to claim 5, whereinthe UTRAN parameter information is supplied by a radio networkcontroller of the UMTS network.
 7. A method according to claim 5,wherein the UTRAN parameter information comprises a list of potentialUTRAN access points.
 8. A method according to claim 5, wherein the userequipment establishes a link through the radio network controller of theUMTS network to a master switching center of the Global System forMobile communication network.
 9. A method according to claim 5, whereinpotential links supplied in a list to the user equipment on whichsatisfactory communication is not possible are deleted from a list ofavailable links.
 10. A method according to claim 5 further comprisingswitching directly from a mode in which the user equipment is incommunication with a Global System for Mobile communication base stationto a UMTS diversity mode in which the user equipment is in communicationwith a plurality of UMTS access nodes.
 11. A method according to claim10, further comprising configuring the UTRAN so that a plurality of UMTSaccess nodes are prepared to communicate with the user equipment.
 12. Amethod according to claim 11, further comprising supplying a list ofpotential UMTS access nodes to the user equipment.
 13. A methodaccording to claim 5, further comprising communicating informationsimultaneously or quasi-simultaneously via both networks during handoverfrom one network to the other.
 14. A method of handing over a GlobalSystem for Mobile communication call to a UMTS network comprising:passing a handover request from the Global System for Mobilecommunication network to a radio network controller of the UMTS network;interpreting the request in the radio network controller; initiatingcall setup; performing radio link setup; performing data link to theUMTS core network; forwarding handover information containing UTRANparameters to user equipment, and setting up a UMTS call based on theUTRAN parameters in the user equipment, wherein the UTRAN parameterspass transparently through the Global System for Mobile communicationnetwork.
 15. A radio network controller of a UMTS network comprising:means for translating Global System for Mobile communication callparameters to UTRAN parameters; means for allocating UTRAN resourcescorresponding to the Global System for Mobile communication callparameters; and means for enabling handover of a call from a GlobalSystem for Mobile communication network to the UMTS network.
 16. Theradio network controller of a UMTS network according to claim 15,further comprising means for performing radio link setup in response toa request from a Global System for Mobile communication network tohandover a call.
 17. The radio network controller of a UMTS networkaccording to claim 16, further comprising means for setting upcommunication with a UMTS core network following successful radio linksetup.
 18. The radio network controller of a UMTS network according toclaim 17, further comprising: means for sending UTRAN parameters to userequipment via a Global System for Mobile communication network; andmeans for enabling the user equipment to establish UMTS communication totransfer the call from the Global System for Mobile communicationnetwork to the UMTS network.
 19. The radio network controller of a UMTSnetwork according to claim 18, wherein the parameters include a list ofpotential UMTS access nodes.